How to Choose the Right Grout Joint Size for Floor and Wall Tile
The Bottom Line:
Grout joint size is determined by the facial dimension variance of your tile, with the TCNA and ANSI standards requiring joints at least three times the tile's size variation, meaning rectified tiles can use 1/8 inch joints while calibrated and non-rectified tiles typically need 3/16 inch or larger, with a minimum of 1/16 inch in all circumstances.
Quick Summary
You have been there. The architect or designer specifies a 1/16 inch grout joint. The tile arrives. You open the boxes. The tiles are not perfectly uniform. Some are slightly wider. Some are slightly narrower. You try to set them with a tight joint. The grout lines wander. They look crooked. The customer is unhappy. You are unhappy.
Here is the truth. Grout joint size is not a design choice. It is a mathematical requirement. The TCNA Handbook and ANSI standards are clear. The grout joint must be at least three times the facial dimension variance of the tile. If your tile varies by 1/16 inch, your grout joint must be at least 3/16 inch. No exceptions.
This guide is for contractors who need to understand the standards, who need to explain them to architects and customers, and who want to stop fighting tile that does not fit into impossibly tight joints.
Let us get to work.
The Math Behind Grout Joint Size
Here is the simple rule that every contractor must know. TCNA Handbook Section "Grout Joint Size, Layouts, and Patterns," excerpted from ANSI A108.02-2017, section 4.3.8, states that to accommodate the range in facial dimensions of tile supplied, the actual grout joint size shall be at least three times the actual variation of facial dimensions of the tile supplied.
That sounds technical. Here is what it means in plain English.
Step 1: Measure your tile. Take a sample of tiles from different boxes. Measure their width and length. Find the difference between the smallest tile and the largest tile. That is your facial dimension variance.
Step 2: Multiply by three. Take that variance and multiply it by three. That is your minimum grout joint size.
Step 3: Check the absolute minimum. The TCNA Handbook states that in no circumstance shall the grout joint be less than 1/16 inch. That is the absolute floor.
Here is an example. If your tile has a total variation of 1/16 inch in facial dimensions, a minimum of 3/16 inch grout joint shall be used. If your tile varies by 1/8 inch, you need a 3/8 inch grout joint. The math is that simple.
Why Tighter Joints Are Not Better
Many customers and designers want tight grout joints. They think it looks more modern. They think it means better quality. They are wrong.
A tight grout joint does not hide imperfections. It exposes them. When tiles vary in size, a tight joint magnifies those variations. A 1/16 inch difference in tile size becomes a 50 percent variation in a 1/8 inch grout joint. That is immediately noticeable and unattractive.
A wider grout joint gives the tile room to breathe. It accommodates building movement, thermal expansion, and the natural variation in manufactured tile. It also allows for warpage that may be present in large tile.
According to the TCNA, a smaller joint will exacerbate the differences between tiles as the human eye can readily see very small differences as a percentage of the total grout joint. A 1/16 inch difference on a 12 inch tile may seem small, but it is readily apparent compared to a 1/8 inch grout joint.
When you explain this to a customer, use this line. "A tight joint does not make the tile look better. It makes the imperfections in the tile look worse. A wider joint is the sign of a professional installation."
Tile Types and Their Recommended Grout Joints
Different tiles have different manufacturing tolerances. Here is how they break down.
Rectified Tile
Rectified tiles are mechanically cut after firing. The edges are precisely square. The dimensional tolerances are tight. Rectified tiles allow for the smallest grout joints.
Recommended grout joint. 1/8 inch minimum. For large format rectified tiles, some manufacturers recommend 3/16 inch for the most successful installation.
When to go larger. If you are using an offset pattern with tiles longer than 15 inches, go to 3/16 inch to reduce lippage.
Calibrated and Non-Rectified Tile
Calibrated tiles are pressed but not mechanically finished. The edges may vary slightly in size. Traditional pressed, cushioned edge tiles fall into this category.
Recommended grout joint. 3/16 inch minimum for most non-rectified porcelain floor tiles. For non-rectified wall tiles, the recommended joint ranges from 1/16 inch to 3/16 inch depending on the specific tile.
When to go larger. For offset patterns, the grout joint should open up to 1/4 inch for tiles with any side greater than 12 inches.
Quarry Tile
Quarry tiles are extruded, not pressed. They are known for having significant dimensional variations.
Recommended grout joint. 3/8 inch. Wider joints accommodate these variations and allow for proper alignment.
Natural Stone
Natural stone varies in thickness and size. The Marble Institute of America specifies that joint width tolerance is the greater of either 1/16 inch or 25 percent of the specified joint width.
Recommended grout joint. Typically 1/8 to 1/4 inch depending on the stone. Always check the manufacturer's recommendations.
Glass Tile
Glass tile is highly expansive. The TCNA Handbook notes that one of the reasons listed for a minimum requirement for grout joint size on all tile installations is thermal expansion, and glass tile is highly expansive.
Recommended grout joint. Follow the manufacturer's instructions. Generally, 1/16 to 1/8 inch.
Grout Joint Size Chart
Here is a quick reference for the most common tile types and sizes.
Large Format Tile Grout Joint Requirements
Large format tile (any tile with at least one side longer than 15 inches) has special considerations.
The minimum. All ceramic and stone large format tile requires a minimum 1/16 inch grout joint according to ANSI. However, that is the absolute floor. Daltile recommends that large tiles have a 1/8 inch or 3/16 inch minimum grout joint for the most successful installation.
The reason. Larger tiles can vary in size more than 1/16 inch. ANSI A137.1 states the maximum caliber range for tiles over 6 inches is 2.0mm or 5/64 inch. According to this standard, the grout joint width is allowed to be three times the facial dimension variance of the tile.
The offset problem. Tile longer than 15 inches tends to have slight variations that cause complications in a brick joint pattern. If the overlap is placed at 50 percent, the joint will bring together the ends of the tile, where there is less bowing, and the center of the neighboring tile, where the bowing is at its greatest. That makes for a floor that will tend toward unevenness.
The solution. If the stagger of the brick joint pattern will be greater than 18 inches, ANSI and Daltile recommend that the offset not be greater than 33 percent to avoid unevenness. Daltile also recommends a minimum grout joint of 3/16 inch to decrease any unevenness in large and heavy tile installations.
Pattern Considerations
Your layout pattern affects your grout joint size.
Stacked Pattern
A stacked pattern has no offset. The tiles align perfectly in a grid. This pattern tolerates tighter joints because there is no offset to magnify warpage.
Recommended grout joint. Whatever your tile's facial dimension variance requires. For rectified tile, 1/8 inch works.
Running Bond (Brick Pattern)
A running bond pattern offsets each row by 50 percent. This is the most common pattern for wood look planks.
The problem. A 50 percent offset brings the high point of one tile next to the low point of the next. This creates lippage.
The solution. For tiles with any side longer than 15 inches, ANSI recommends that the offset not be greater than 33 percent. The grout joint should also open up to accommodate warpage. For tiles longer than 12 inches, the grout joint should open up to 1/4 inch when using an offset pattern.
Herringbone and Chevron
These patterns create angled cuts. The tiles interlock. There is less room for error.
Recommended grout joint. At least 3/16 inch. For natural stone, 1/4 inch or larger.
Grout Type vs Joint Size
The size of your grout joint determines what type of grout you can use.
Unsanded grout. For joints smaller than 1/8 inch. Unsanded grout does not have sand aggregate, so it can fit into tight joints without scratching the tile. It is also recommended for marble and other soft stones that can be scratched by sand.
Sanded grout. For joints of 1/8 inch and larger. Sanded grout is stronger and more durable than unsanded grout. It is the standard for most floor tile installations.
Wide joint grout. For joints larger than 3/8 inch. Some manufacturers sell a wide joint mix, or you can add coarse sand to regular grout.
Epoxy grout. For any joint size. Epoxy grout is stain proof and waterproof. It is more expensive and harder to apply, but it lasts longer.
How to Determine Your Tile's Facial Dimension Variance
You cannot guess this. You have to measure.
Step 1: Open multiple boxes. Take tiles from at least three different boxes. Different boxes may have different dye lots and different sizes.
Step 2: Measure each tile. Measure the width and length of each tile. Use a caliper or a precise tape measure. Measure at multiple points.
Step 3: Find the range. Find the smallest tile and the largest tile. Subtract the smallest from the largest. That is your facial dimension variance.
Step 4: Multiply by three. Take that variance and multiply by three. That is your minimum grout joint size.
Step 5: Check the manufacturer's recommendation. Some manufacturers specify a minimum grout joint on the box. Always follow the manufacturer's recommendation. It is usually more conservative than the TCNA minimum.
Common Grout Joint Mistakes That Cost Contractors Money
I see these mistakes on job sites constantly.
Mistake 1: Letting the architect or designer specify a joint that is too tight. The architect specifies 1/16 inch because it looks modern. The tile has a 1/16 inch facial dimension variance. That means the minimum joint is 3/16 inch. You try to install at 1/16 inch. The grout lines wander. They look crooked. The customer is unhappy.
The fix. Before you start, measure the tile. Calculate the minimum joint size. Show the math to the architect and the customer. Explain that a tighter joint will look worse, not better. Get the joint size changed in writing before you start.
Mistake 2: Not checking tile size variation. You assume all the tiles are the same size. They are not. You set them with a tight joint. Halfway through the job, you realize the tiles are not fitting. You have to adjust your joint size mid job. The grout lines are inconsistent.
The fix. Check the tile size variation before you start. Measure tiles from multiple boxes. Calculate your minimum joint size. Then set your spacers accordingly.
Mistake 3: Using the wrong grout for the joint size. You use unsanded grout in a 1/4 inch joint. The grout shrinks. It cracks. It fails.
The fix. Match your grout to your joint size. Unsanded for joints under 1/8 inch. Sanded for joints 1/8 inch and larger.
Mistake 4: Not accounting for offset patterns. You use a 50 percent offset with a 1/8 inch joint on a 12x24 inch plank. The lippage is terrible.
The fix. For tiles with any side longer than 15 inches, limit your offset to 33 percent maximum. Open your grout joint to 3/16 inch or larger.
Mistake 5: Grouting movement joints. You fill the perimeter gap with grout instead of sealant. The floor expands. The grout cracks. The floor buckles.
The fix. Perimeter joints and other movement joints must be filled with flexible sealant, not grout.
What to Do When the Customer Wants a 1/16 Inch Joint
This is a conversation every contractor dreads. Here is how to handle it.
Step 1: Explain the math. Show the customer the TCNA standard. Explain that the grout joint must be at least three times the facial dimension variance of the tile.
Step 2: Show the risk. Explain that a tighter joint will show every imperfection in the tile. The grout lines will wander. The floor will look crooked. A wider joint will hide those imperfections and look better.
Step 3: Offer options. If the customer absolutely insists on a 1/16 inch joint, offer to order rectified tile. Rectified tile has tighter tolerances and can handle a 1/8 inch joint. But even rectified tile may not handle 1/16 inch. Be honest about the limitations.
Step 4: Get it in writing. If the customer insists on a joint that is smaller than the TCNA minimum, get it in writing. Have them sign a waiver. Explain that you are not responsible for the results.
Quick Reference Table: Minimum Grout Joint by Tile Type
Frequently Asked Questions
What is the minimum grout joint allowed by TCNA?
The TCNA Handbook states that in no circumstance shall the grout joint be less than 1/16 inch. However, the actual joint must be at least three times the facial dimension variance of the tile.
Can I use a 1/16 inch grout joint with rectified tile?
Possibly. But you must measure the tile first. If the tile has a facial dimension variance of 1/32 inch or less, a 1/16 inch joint might work. But many rectified tiles have a variance of 1/16 inch, which requires a 3/16 inch joint. Always measure before you commit.
What grout joint should I use for 12x24 inch tile?
For 12x24 inch non-rectified tile, use a 3/16 inch grout joint minimum. For rectified 12x24 inch tile, 1/8 inch is acceptable. If you are using an offset pattern, consider 3/16 inch to reduce lippage.
What grout joint should I use for 24x48 inch tile?
For 24x48 inch tile, use a minimum of 3/16 inch grout joint. The large size means more warpage and more movement. A wider joint accommodates that.
Does grout joint size affect the strength of the installation?
Yes. A wider joint is stronger because there is more grout to support the tile edges. A tight joint is weaker and more prone to cracking.
Can I use sanded grout in a 1/16 inch joint?
No. Sanded grout is for joints 1/8 inch and larger. Use unsanded grout for joints under 1/8 inch.
What if my tile varies by more than the manufacturer claims?
It happens. Tile manufacturers sometimes ship tile with about 3/32 inch difference between the largest and smallest tiles in a box. Always measure your tile before you set your joint size. Do not trust the box.
A Final Word From The Tile Shoppe
Grout joint size is not a design choice. It is a mathematical requirement. The TCNA and ANSI standards are clear. The grout joint must be at least three times the facial dimension variance of the tile. No exceptions.
When you explain this to a customer, you are not being difficult. You are being professional. You are protecting them from a failed installation. You are protecting yourself from a callback.
At The Tile Shoppe, we sell the tile, the grout, and the spacers. But we also sell knowledge. We want your installations to succeed. We want you to get referrals, not callbacks.
So next time an architect specifies a 1/16 inch joint, do not panic. Measure the tile. Do the math. Explain the standards. And if they still insist, get it in writing.
Your reputation depends on it.
Now go lay some tile. And leave room for the grout.
